1. Field of the Invention
This invention relates to a waveform modulator, and more particularly to an optic intensity modulator.
2. Description of Related Art
Currently, fiber optic sensors have been developed for a wide range of applications, in which a time division multiplexing (TDM) technology is a typical technology used in modern communications and fiber optic sensor network. TDM of the fiber optic sensor network has advantages of low crosstalk and simple construction. Particularly, TDM of fiber optic interferometric sensors has been shown to have the lowest crosstalk and optimum sensitivity as referred to a published paper on "J. Lightwave Technol., LT-5,pp. 1014-1023, 1987". In a TDM fiber optic sensor system, a continuous-wave laser source can be externally modulated by an intensity modulator to generate an optic pulse. The output optic pulse of the intensity modulator with high extinction ratio (ER) is a key issue to increase the sensor sensitivity and to reduce the sensor crosstalk, especially for a TDM fiber interferometric sensor system, as referred to a published paper on J. Lightwave Technol., VOL. 14, NO.6, 1488-1500,1996.
It is very important in a TDM fiber optic sensor system to select an intensity modulator with high ER (typical ER.gtoreq.30 dB) and to control the output optic pulse of an intensity modulator with optimum ER.